The alignment of systems comprising a mechanical part is a problem appearing at the same time as the systems themselves. As is known per se, digital adjustment methods especially equate existing experimental points and find application in fields where the precise alignment of systems comprising a machine or a device is essential.
By way of example, there is the field of printing and in particular machines comprising a plurality of printing heads. In fact, the diversity of applications engendered by the possibilities of these machines needs the majority of time the presence of several printing heads within the same machine. But for the operation of the printing machine to be optimal, these heads must be aligned with precision close to the resolution of printing, involving micrometric adjustments. Therefore, adjustment via digital methods makes perfect sense.
Many methods reducing artefacts linked to poor alignment of mechanical systems depending on each other are described in the prior art.
A particular example is document WO 2005/039881, disclosing a method for alignment of printing heads comprising each a plurality of nozzles. To form a pattern which will serve as alignment of the heads, each printing head prints on a substrate a series of drops. After acquisition and digitisation of this pattern, computer means calculate the distance between each series of points and compare them to an ideal distance, characteristic of optimal alignment between the heads. The result of this comparison acts as a basis for alignment of the printing heads relative to a reference head. However, this digital adjustment method is done on isolated printing marks.
Another example is document US 2011/0169893, which discloses an ink jet printing machine comprising adjustment means of the alignment of the substrate. At least one printing head makes a pattern composed of specific points, said pattern being later digitised by acquisition means contained in the printing machine. This digital image is then analysed, the position of the points being compared to the position of points within the scope of optimal alignment. The result of this comparison acts as a basis for alignment of the substrate by means of adjustment means. However, and as previously, the digital adjustment method is carried out on isolated printing marks. On the other hand, it is not the printing heads, but the printing substrate which needs to be aligned.